Capacity controlled amplifier



July 11, 1933. c. D. BARBULESCO El AL 1,917,237

CAPACITY CONTROLLED AMPLIFIER Filed May 14, 1929 Capacifg Z. [d aft 3%Pay? JK war I Patented July 11, 1933 UNITED STATES PATENT OFFICECONSTANTIN D. BAIRBULESCO AND PAUL S. EDWARDS, OF DAYTON, OHIO CAPACITYCONTROLLED AMPLHIE'R Application filed an 14, 1929. Serial No. 368,019.

(GRANTED UNDER THE ACT OF MARCH}, 1888, AS AMENDED APRIL 30, 1928; B700. G. 757) existed with amplifiers of the ordinary type is that theyhave little amplification per stage and it has therefore been necessary,in order to secure proper amplification, to em ploy several stages allof which increases cost,'complication and frequent servicing.

Another difiiculty which has heretofore existed in ordinary amplifiersis that they are unstable, require close attention in operation, andfrequent adjustment.

An object of this invention is to provide an amplifier of enormousamplification and great stability.

Another object of this invention is to de vise an amplifier whichoperates only in one direction and will not feed back the energyamplified in consecutive stages if this efiect is not desired.

Still another object of this invention is to provide a capacitycontrolled amplifier of the electronic tube type that is simple inconstruction, positive in action and requires little attention oradjustment in operation.-

With these and other objects in view which may be incident to ourimprovements, the

invention consists in the parts and combinations to be hereinafter setforth and claimed,

with the understanding that the several necessary elements comprisingour invention may be varied in construction, proportion and arrangement,without departing from the spirit and scope of theappended claims.

In order to make our invention more clearly understood we have shown inthe accompanying drawings means for carrying the Prior to this time thedifliculty which has same into practical effect, without limiting theimprovements in their useful application to the particularconstructions, which, for the purpose of explanation, have been made thesubject of illustration.

In the drawing:

Fig. 1 is a diagramof one form of our improved amplifier showing theseveral circuits and elements involved.

Fig. 2 is a, graph showing the shape or pattern of the group of highfrequency oscillations generated by our improved device. Fig. 3 is agraph showing the points of operation of our device on the resonancecurve.

Fig. 4 is a diagram of a modified form of circuit adaptedfor regulation.

Referring by numerals to the drawing, wherein the same elements aredesignated by like symbols, and more particularly to Fig. 1, there isshown a measuring instrument 1, provided with anindicating needle 2,playing over a graduated scale 3. Needle 1 and a magnetic segment ofsmall capacity 4 are attached to a moving element 5 pivoted for rotationin a magnetic field 6. A stationary insulated metallic plate 7 of smallcapacity is mounted to coact with metallic segment 4.

The instrument 1 is of the most sensitive type; it can detect minutecurrents of any kind and by the displacement of the needle it produces avariation in the capacity between the metallic plates 4 and 7. The smallcapacity 4 and 7 is connected in parallel with the oscillating circuit 8and 9, which is tuned close to resonance with respect to the tankcircuit 10 and 11 associated witha selfmodulated oscillator. Theoscillator comprises an electronic tube having a filament 20, a grid 21and a plate 22 contained in a vacuum container 23. Numerals 12, 13 and14 indicate the choke coils producing the driving electromotive forcenecessary to maintain high frequency oscillations in the tank circuit 10and 11. Numeral 15 indicates a blocking condenser, and 16 a resistanceof large value. The condenser 15 is charged by high frequencyoscillations and discharges periodically in the resistance 16. Thenumorals l7 and 18 indicate batteries or other sources of direct currentand 19 indicates a meter in circuit with tube plate 22.

Fig. 2 shows the shape of the group of high frequency oscillationsgenerated and Fig. 3 shows the two possible points of operation, A andB, on the resonance curve. These points are selected at the two pointsof inflection of the curve in order to have the greatest varialt tion,A1,, in plate current for the minimum variation, AG in capacity producedby the displacement of the metallic plate 4.

lit may be readily appreciated that meter 19 can be provided with asystem of plates M5 similar to 2 and d (as shown in Fig. 4:) and anotherstage added in cascade; the number of additional stages being limitedonly by the amount of power to be disposed of in the plate of the lasttube.

llt is also evident that a relay can be used instead of the meter 19 andstill greater amount of power controlled by a slight displacement of themetallic plate l.

The great advantage of this scheme oi amplification is the impossibilityof any kind of feed back unless this eilect is desired. It regenerationis desired it can be easily produced by the simple arrangement shown inFig. 4, in which the meter 19 is provided 39 with a pair of plates 24and 2!") similar to d and Y. The extra capacity due to these plates isput in parallel with the input circuit 8 and 9.

lit an increase in the capacity of 8 pro- 35 duces a decrease of theplate current it is evident from the movement of the needle 26 that thecapacity between 24 and 25 increases and adds to the increase incapacity produced by the external cause. A still further de- 443 creasein plate current is produced and the efiect is still further amplified.

lit the fined plates 7 and 25 are placed at the left of the movingplates 4 and 24, the reversed efiect will take place, which means that adeflection to the right of the needle 2 will add more capacity to 8 andit the op erating point is A an increase in the plate current will occurand the needle 26 will move to the right, adding by the approach of the59 plates a still greater increase in the capacity 8 and consequently afurther increase in the plate current.

While we have shown and described the preferred embodiment of ourinvention, we wish it to be understood that we do not conline ourselvesto the precise details of arrangement herein set forth by way ofillustration, as it is apparent that many changes and variations may bemade therein by those 133 skilled in the art without departing from thespirit of the invention, or exceeding the scope of the appended claims.

We claim: 1. In a system of amplification, aselfmodulating highfrequency oscillator, an ex Bil nerves? ternal oscillating circuitcoupled to said oscillator, a variable condenser associated with saidexternal oscillating circuit to vary its natural frequency and anauxiliary variable condenser associated with said external oscillatingcircuit to slightly vary its frequency and hence to vary the amount ofcurrent flowing in the plate circuit of the oscillator.

2. lln a system of amplification, a self-modulating high itrequencyoscillator, an indicating instrument, a variable condenser associatedwith said instrument to be varied thereby, an external oscillatingcircuit coupling said condenser to said oscillator, whereby a deviationof the indicating instrument will cause a variation in current in theplate circuit of the oscillator.

' 3. In a system of amplification, a selfmodulating high frequencyoscillator, an indicating instrument in the plate circuit of saidoscillator,'and a variable condenser associated with said instrument toindicate variations in the plate current of the oscillator by variationsin the capacity of the variable condenser.

l. In a system of amplification, a sellniodulating high frequencyoscillator, an input oscillating circuit tuned close to resonance withand coupled to said oscillator, an indicating instrument in the platecircuit of said oscillator, a variable condenser associated with saidinstrument to be varied thereby, said variable condenser being connectedto said input oscillating circuit, whereby variations in the platecurrent of the oscillator will be reflected in variations in the naturalfrequency of the input oscillator circuit.

5. A system of cascade amplification comprising, a self-modulating highfrequency oscillator, an input oscillating circuit coupled to saidoscillator and tuned close to resonance therewith, an indicatinginstrument for measuring the controlling current for the amplitier, anda variable condenser connected with said instrument to be operatedthereby, said condenser forming a part of the input oscillating circuit,whereby slight variations in the controlling current will cause largevariations in the plate current of the oscillator through theintermediary of the variable condenser and the input oscillatingcircuit.

6. In an amplifier, in combination, a sellmodulating high frequencyoscillator, an external oscillating circuit coupled with and tuned closeto resonance with said oscillator,

means for varying the capacity of said exter nal, oscillating circuit toproduce variation of the plate current of the oscillator, and means forvarying the plate current of the oscillator to vary the capacity of theexternal oscillating circuit to produce further variation of the platecurrent.

7. In an amplifier, in combination, a selfated by variations in theplate current of the oscillator for varying the capacity of saidvariable condenser.

In testimony whereof we aflii: our signatures.

CONSTANTIN D. BARBULESCO. PAUL S. EDWARDS.

